VacuMed "Vista" Metabolic Measurement Systems

Competitor Qualification Checklist

Which system is most accurate and how is the accuracy claim substantiated?

Was the sales person able to answer all my questions?

Who has the best Performance Guaranty?

Which instrument will cost me least to maintain over the next 5 years?

Which system uses the flow sensor least affected by gas conditions,
such as temperature, humidity, viscosity and specific gravity.

When checking references, don't just ask "Have you had any problems?" After all, everyone uses commercial components and once in a while one will fail. The question is "How did the manufacturer respond to the problem?" and "How long did it take to fix it?" and "How much did it cost?"

This is a delicate subject. If VacuMed does not come out on top, you may need to go back a couple of chapters and study the material presented.

People ask us "The price of your VO2 measurement systems is so much less than the competition, how can it be better?"

VacuMed guarantees the accuracy of the VO2 and VCO2 measurement to be better then +/- 3% of the reading.

There are instruments that cost a lot more than ours, but do you get more? We have tested many of the well known, expensive instruments and we cannot remember ever testing one that was as accurate as our own metabolic measurement systems.

Here is how we test our system:
We use an improved version of the Huszczuk-Whipp-Wasserman Metabolic Calibrator
described in the CALIBRATION section. We maintain that this is the only valid accuracy verification method.

We have seen competitors make accuracy claims without explaining how accuracy is determined. But the majority simply makes no claim at all. They try to impress you with grandiose specifications of their gas analyzers, but no mention is made of the accuracy of the VO2 and VCO2 measurement.

Some instruments present you with a special feature: Contrary to the way most conventional systems work, and contrary to the method most published data is obtained, they measure INSPIRED volume rather than expired volume. They make some almost believable claims: Inspired volume (or flow) is easier to measure because temperature and humidity is equal to ambient. At first glance this is almost convincing until you ask some questions, such as:

What's more reliably determined, ambient humidity or exhaled humidity,
which is always 100%?

Inspired volume is not equal to expired volume,
so how do you calculate expired volume which matters more than the inspired one.

The measurement of inspired* volume always presumes the use of a two-way breathing valve, which increases resistance, deadspace and ignores the fact that ALL such valves leak to some extent, mostly at low flows, so REE or BMR measurement accuracy is affected.

Some competitors claim to use the Douglas Bag method to validate their devices. But the Douglas Bag method has a repeatability of around 5%, so what kind of validation is this? How can one validate one measuring method with another more primitive and antiquated?

So why is our instrument lower priced?
First of all, large companies have a huge overhead: You may be paying for the president's private plane, fancy offices, huge salaries and bonuses. Secondly, they may offer features, such as Nutritional Assessment of patients on a ventilator, that are very costly to support. Instruments in an Intensive Care Unit require 24-hour service support, training and retraining of several shifts of nurses and technicians. The price of the instrument reflects this overhead; you pay for it even though you have more modest expectations. Finally, our prices are broken down on a component basis, so if you already have a computer, or if you do not want a cart, you don't buy it.

VacuMed does not support Nutritional Assessment of patients on a ventilator.

* The same valve-leaking problem exists with the expired only flow measurement, which is required with full-size mixing chamber systems. In other words, the two-way breathing valves commonly used to separate respiratory flows always leak, causing a 2 - 7% underestimation of tidal volumes, thus minute ventilation.